Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

This adds substantial behavior beyond the annotations: it returns shares and bands only (no volumes), it protects against control failures and refuses the run without charging when one fails, and every result carries a run id, date and citation line. It also describes the two-step payment flow (this call returns a payment_url and price; the paid run happens over MPP or x402). The payment messaging is slightly tangled, because it says both 'this tool charges nothing' and '$3.00 per run, charged only when the run comes back sound', which costs it a point on clarity.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The definition is front-loaded well: triggers first, then output, then trust/limits, then price. However, the payment mechanics are repeated: MPP and the Stripe shared payment token appear twice, as does the $3.00 price, and the 'charges nothing' versus '$3.00 per run' phrasing makes the reader re-read. The sample JSON link is a useful, earned sentence.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a single-parameter, read-only tool with no output schema, the definition covers what an agent needs: the trigger, the metric and its window, the verdict vocabulary, the modifier-level trend, the 'shares and bands only' limitation, citations/run id provenance, refusal behavior, and cost. The free sample URL compensates for the absent output schema.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

There is only one parameter, and the schema documents it fully ('The brand as people search for it'), so the schema does the heavy lifting. The description marginally enriches meaning by framing everything as US Google search share, which implies the brand string should be the consumer-facing search term. It adds no format or disambiguation guidance beyond that.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb and resource: it returns the share of a brand's US Google searches using cheaper-way-in modifiers (price, cheap, discount, coupon, dupe, alternative, sale) versus the prior year, plus a verdict of eroding/holding/strengthening. That is far more precise than the title's question form. It never names a sibling tool, though, so the boundary against run_demand_check, run_share_of_search and run_deal_activity has to be inferred from the metric definition alone.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The opening sentence gives explicit trigger conditions: the user asks whether a price premium is holding, whether customers are trading down, or whether a price rise is hurting demand. That is concrete when-to-use guidance. It gives no when-not guidance and never names an alternative tool for adjacent questions.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.